Summary: Enzymes involved in pyruvate metabolism were assayed in crude extracts of cells grown photosynthetically with different carbon sources. Pyruvate dehydrogenase, pyruvate carboxylase, pyruvate kinase and phosphopyruvate carboxykinase (ATP) were all present in extracts of cells grown on -lactate, whereas phosphopyruvate carboxylase, phosphopyruvate synthase and pyruvate, orthophosphate dikinase were undetectable in extracts of cells grown on either -lactate, -malate or acetate. Malate-grown cells and acetate-grown cells contained lower levels of pyruvate carboxylase and higher levels of pyruvate kinase than did lactate-grown cells, and malate-grown cells also contained lower levels of phosphopyruvate carboxykinase. Pyruvate dehydrogenase activity was undetectable in extracts of acetate-grown cells. Two mutant strains, which were unable to grow on pyruvate, lactate or any other compound metabolized via pyruvate, were found to be deficient in pyruvate carboxylase activity, indicating that this anaplerotic enzyme is essential for growth on pyruvate or related compounds as sole added carbon source. This requirement for pyruvate carboxylase can be bypassed to some extent, however, since the mutants grew on acetate, albeit more slowly than the wild-type and after a long lag period. The key enzymes of the glyoxylate cycle, isocitrate lyase and malate synthase, were present at high levels in extracts of acetate-grown cells, both of the mutants and of several wild-type strains tested, whereas isocitrate lyase activity was undetectable in three different strains of This is consistent with previous suggestions that acetate is assimilated via the glyoxylate cycle in but not in


Article metrics loading...

Loading full text...

Full text loading...


Most cited this month Most Cited RSS feed

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error